A person naturally produces sebum (from the sebaceous gland) and other oils from the face and fingertips. A person deposits such oils on cell phone (or other article) display screens, such as glass (or a screen protector, typically a polymeric plastic), glass ceramic, metal oxide, Plexiglas or the like materials or surfaces. Often. Such oils are visible and can reduce the quality of the images seen on the device, as well as contribute (with dirt, dust, etc.) to a reduced aesthetic appearance of the screen. Invisible fingerprint (“IFP”) coatings are generally oleophilic coatings that cause oils to be invisible, or nearly invisible, by causing the oils, e.g., from fingerprints, to spread along the screen surface. The oils will match the index of refraction of the screen material, e.g., glass, so that light passes through making it appear that there are no fingerprints. The fingerprints are still present, one just cannot see them (at least not without scrutinizing the surface). Coatings and coating materials displaying IFP properties need to be hydrophobic enough that the oils bead up and evaporate. If the coating is too hydrophilic, then one can see the fingerprint. Also, if the coating is too hydrophobic (e.g., contact angles greater than about 85 degrees), it does not exhibit adequate properties.
In contrast, “anti-fingerprint” (“AFP”) coatings are oleophobic coatings that resist wetting and can make fingerprints which do form more easily cleaned, but do not prevent formation of fingerprints or reduce the conspicuousness of fingerprints that do form. IFP coatings function in a different manner than AFP coatings.
It would be desirable to have a coating that can provide optically transparency, mechanically durability, and invisible fingerprint properties.